# A drainage ditch alongside a highway with a 3% grade (drops 3 mfor every 100 m of

## Question:

A drainage ditch alongside a highway with a 3% grade (drops 3 mfor every 100 m of length) has a rectangular cross section of depth1.35 m and width 2.5 m. To prevent soil erosion, the ditch isfilled with rock fragments with an average effective diameter of12.5 cm. The rocks are packed such that 56% of the ditch volume istaken up with rock and the remaining portion is open forflow.

a) During a rainstorm, what is the maximum capacity of the ditch(m3/min) if the water just reaches the top of the ditch?

b) At this condition, is the flow through the bed laminar orturbulent? Prove with a calculation. c) To further back up youranswer in b), calculate the percents error in the volumetric flowrate calculation in a):

i) if you had assumed the flow was laminar, and ii) if you hadassumed the flow was turbulent

**Related Book For**

## College Physics A Strategic Approach

ISBN: 9780134779218

4th Edition

Authors: Randall D. Knight, Brian Jones